Hi
I have a Golf Mk4 1.6 which is very hesitant when excellerating. My VW dealer are trying to sort out this fault; they have put a new Throttle Body and Lampda Probe or sensor, not sure which, but the car still hesitates and it jerks along brilliantly when crawling in traffic. When I took it back to the Dearler last Saturday they had it for over 7 hours and then decided to try new battery on the car as they felt that under load the battery was losing power.
Has anybody heard of this sort of problem? I did say that if battery not holding charge would that not be the alternator? VW said no.
I did speak to a garage who deal with electrical problem with cars and they did mention the engine management system may be the problem.
I am totally lost at what to do, my warranty runs out end March and this fault isnt going away. Can car computers be re-booted like personal computers?
Any advise would be very much appreciated.
Thanks Noel
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To be honest I can't really see why the battery would need to be replaced. It should be fairly easy for them to check battery condition and alternator output. Sounds like they are clutching at straws. If it hesitates when accelerating under load then I would suspect HT side is the problem.
In a sense an ECU 'reboots' every time you turn on the ignition. However it has no secondary storage (like a HDD) and there is no operating system to load (as there is in a PC) - all the software is stored as 'firmware' in flash EPROM chips. VW can reinstall the software, but that should not be necessary.
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To be honest I can't really see why the battery would need to be replaced. It should be fairly easy for them to check battery condition and alternator output. Sounds like they are clutching at straws. If it hesitates when accelerating under load then I would suspect HT side is the problem. In a sense an ECU 'reboots' every time you turn on the ignition. However it has no secondary storage (like a HDD) and there is no operating system to load (as there is in a PC) - all the software is stored as 'firmware' in flash EPROM chips. VW can reinstall the software, but that should not be necessary.
Are you sure? I was chatting to someone the other day who wrote the software for car ECUs. I'm studying DSMs at uni at the moment and was after help!
Amongst other things he told me that they continuously adapt to driving style and input from engine sensors. In fact, when you switch off the ignition the ECU remains active for about 30 minutes, refining and checking its thermal model of the engine as it cools down.
A lot of what happens in the ECU is dynamic... in fact, about half the code in there is redundancy in case a sensor fails.
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Are you sure? I was chatting to someone the other day who wrote the software for car ECUs. I'm studying DSMs at uni at the moment and was after help! Amongst other things he told me that they continuously adapt to driving style and input from engine sensors. In fact, when you switch off the ignition the ECU remains active for about 30 minutes, refining and checking its thermal model of the engine as it cools down. A lot of what happens in the ECU is dynamic... in fact, about half the code in there is redundancy in case a sensor fails.
Obviously there is a control program for the car, but it will use many variables which are continually modified and refined in response to driving style, engine wear etc etc - in other words the system is 'adaptive'. Normally the ECU will start with default values (often, disconnecting the battery for a few minutes will 'reset' the ECU restore these daefaults) and then these values will be modified over time as the vehicle is used (short & long term fuel trim, idle speed trim etc etc). Sensor data is also checked for 'plausibility' and if 'out of range' (i.e. implausible data) is present then a default value is substituted and the MIL is illuminated. Some manufacturers like Mitsubishi have also made a big play about using 'fuzzy logic' techniques to help improve auto transmission behaviour, for example.
I have not heard of ECU's staying active for 30 mins after switch off - I can't imagine how monitoring the engine cooling down would help. But there are all sorts of developments going on all the time, so I could well be wrong on this!
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Are you sure? I was chatting to someone the other day who wrote the software for car ECUs. I'm studying DSMs at uni at the moment and was after help! Amongst other things he told me that they continuously adapt to driving style and input from engine sensors. In fact, when you switch off the ignition the ECU remains active for about 30 minutes, refining and checking its thermal model of the engine as it cools down. A lot of what happens in the ECU is dynamic... in fact, about half the code in there is redundancy in case a sensor fails.
There's only one heat sensor though, and that checks the temperature of the coolant (Or the head in some cases, the Ford diesel Endura engines for example)
Unless there's something I don't know about brand new cars it sounds like he was talking it up a bit.
I wouldn't mind being proven wrong though, it does sound interesting.
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Thanks for replying.
I had a word with another garage, they said that if the voltage drops below 9.6 this will affect the running.
Ive been on a long journey since VW fitted the battery and its made no difference to the hesitating problem when I accelerate.
So the cars goes back to VW to have new battery removed and my old one replaced back on. I did mentioned to VW about using Optimax Fuel and they said this may work, but I need to do it for a month and its expensive!
I did read off the internet that my model Golf doesnt have HT leads but coil packs and I know if this go its very noticable. So I was wondering if it might be the injectors, so I put some Redex in and hope this works. As my car is still under Warranty the injectors are covered, I think, but I cant ask the Dealer to replace them as they have to find the fault with them, dont they?
Anyway sorry to go on but this must be the worst fault a modern car gan get. Wish I got a classic car instead.
Noel
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I had a similar problem when accelerating where the car would jerk (quiet violently) as if it had lost power. I had it in the garage a few times until they discovered that the air filter was wet and replaced never had any issues after that.
Hope this helps.
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I had a similiar problem with Pug 306 1.6 petrol. It turned out to be the HT leads, despite there being no fault found when they were tested by the diagnositc equipment. The vibration of running on the road affected their function which wasn't picked up when testing with the car stationary.
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you could try taking the earth lead off the battery (the neg one)that should re-set the ecu back to default. try it? it worked ok on my vauxhall. leave it off for 1 minute.
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I'm late into this, but . . .
Is the engine misbehaving in a sharp "black or white" cut-out way or in a fluffy and much less sharply defined "stumbling" way? I would think electrics for the former and fuel system for the latter. My most recent experience of the former was when I fitted brand new HT leads to my Capri 2.8i and they were found to be faulty. The latter was characteristic of a cool-running problem I had on an Audi 100, which was cured instantly by the product referred to below.
I'll do my cracked vinyl-record trick again: try VAG's own injector cleaner and see if that helps. If it does, then hooray, and it might be the short-trip syndrome that's causing the problem by gumming things up (the Audi problem). If it doesn't help, it will only do good anyway. You'll need the part number (G 001 700 03) and it's now about £7 a bottle, enough to add to 150 litres of fuel (the price just keeps on rising).
Warning: I am no technical expert and I speak only from this stuff having solved a similar problem for me. If it does work, keep using it at every fill-up if you can. Plus the occasional Italian tune-up, of course (i.e. really push the engine for more than a few miles).
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The problems more of a 'stumbling' way, I think, that why I replaced the fuel filter and a I put some Redex in with the fuel. Havent tried using Optimax yet but seeing as your the third person to suggest it, I'll think I'll give that ago.
Funny you should mentioned short journeys, I did my weekly oil check and the oil filler cap was a creamy colour, I was worried so I called Dealer. They informed me that if I do only short journeys, which I do, this is the cause-condensation mixing with the oil on cap, amazing! Thought I'd blown my head gasket!!
Your mentioned Italian tune-up, is this a tune-up by an Italian, only joking. Seriously, somebody else posted this too, what is it-sorry for being thick?
Noel
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The fact you haver the problem just now and the warranty ends i March is not really a problem (other than getting it fixed)
VW know of the problem and if it takes months to track it down the hesitancy problem will still be under warranty.
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>>The fact you haver the problem just now and the warranty ends i March is not really a problem (other than getting it fixed)<<
definitely agree with that - make sure you advise your dealer that you regard this as a warranty issue yet to be fixed.
I would disregard the ECU for now.
Put the best quality fuel in (Optimax or similar) and make sure that all connectors are properly shut. leave the coils/ht leads upto the dealer. If you can, just leave the car at the dealer till it's fixed
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There have been many problems with coil packs on VW's. They were the subject of recalls. Check whether there have been any replacements on your car. In the light of problems with coil packs I would have thought that this would have been one of the first things to be checked by the garage. Do a search on this forum for coil pack problems.
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Forgot to say - have a look at www.vwaudiforum.co.uk/
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Try flooring(and I mean flooring) the throttle when the engine is idling, does it sound as though it is briefly dropping a couple of cylinders(sounds like a 2cv!), if so then the wasted spark coil pack is probably on its way out.
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I forgot to mention the 1.6 wasted spark coil pack shoul not be confused with the individual (1 per cylinder) troublesome coil packs of the 1.8+(or 1.2 on Polo) . The 1.4 & 1.6(non FSI?) have 1 coil pack consisting of two coils, each coil sparks two cylinders(via ignition leads) one of the sparks being wasted - hence the term "wasted spark".
P.S. If the coil pack totally breaks down it has been known to spike the cars ECU!
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Having just read this thread, I now know for certain that diesels are much better for low milage journeys.
You do not get mayo in the engine, like my wife used to in her petrol Escort. You don't get all these electrical problems with coils, plugs, plug leads etc.
Get a diesel, you know it makes sence. The only problem with a diesel is that it takes longer to warm up, but VW's warm up a bit quicker than Ford's, but Ford's do have an heated windscreen.
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All this talk of optimax is clutching at straws;--- great as optimax might be, a Golf (which might even have been built before optimax was a twinkle in Mr Shell's eye) should run perfectly on normal fuel, if it doesnt then there's a problem.
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My wifes car (golf mk 4-1.6 non fsi) had coil problems at about 3 yrs old, hesitant and jerky and the warning light came on that, upon consulting the inst. manual, told her to take it to her VW workshop/dealer. All the coils have now been replaced,one per cylinder (4) and everything is now OK.
Short journeys could also be the cause though, in which case the "Italian tune up" might be the answer.
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Just read all the replies, thanks.
I have mentioned to VW dealer that maybe to could be coil pack and they said no, I would notice a more servere problem!
Ive had no warning light coming on so maybe they're right.
If I do 'floor it' there is a definate 'flat spot' before the car picks up again.
Dealer seems to be at a loss now as the ECU is showing no fault codes and I feel they dont want to replace things just to elliminate them. So Im going to run it on Optimax for a month, replace the air filter, have a look at the plugs and find a garage that can test my coil packs.
And what is an'Italian tune up!' Will someone explain.
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i once had a golf that was hesitant and jerked badly especially at low speeds and at standstill, i also heard loud buzzing noise from fuel pump area,turned out the car had two fuel pumps, one was a lift pump situated in the tank and the other the main pump, fault was the lift pump in the tank had stopped so the main pump was doing all the work and when at standstill because there was no air rush keeping main pump cool it soon started to overheat causing the hesitance problem, not sure how relevant this is your golf as this was an earlier model.
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I suspect that short journeys aren't helping at all.
By all means try Optimax; although I share the sceptical view above about its likely impact, it is known to have excellent cleaning properties. Do try the VAG injector cleaner as suggested above. Do try an Italian tune-up, which I explained briefly above, but to elaborate a little just think of yourself as a macho Italian wanting to impress his passengers around the roads and hills near Modena -- belt the revs (go to the max line) at every opportunity for a session or two, but don't make a habit of it. In summary, try simple and cheap things first.
And if all that has some effect, try to get out of the short-journey habit if you can. It's an engine killer. Go the long way around and get at least 10 miles each way.
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Thanks for explaining the meaning of 'Italian tune up' I often imagine Im sitting on the starting grid at Monte Carlo!!
I will try the VAG cleaner, as you say simple and cheap first.
I did read that this model golf have faulty power steering switch which can cause hunting and erractic idle-what do you think or am I clutching at straws?
Noel
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Is this Italian Tune Up an excuse when stopped by the police for speeding?
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>>Is this Italian Tune Up an excuse when stopped by the police for speeding?
You can do this without breaking speed limit,means taking 1st gear and second up to speed limiter.ok on some cars they can break limit,just have to use a bit of common sense ie use the revs where you can without causing danger to anyone else or getting nicked for speeding!
--
Steve
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>>that maybe to could be coil pack and they said no>>
Although this was a problem for VW about five years ago due to a supplier's large batch of faulty coil packs, it only related (IIRC) to the 1.8-litre engine.
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Further to the 1.6 VW engine - I have the same engine in my Bora and it does occasionally seem to hesitate, especially on idle.
Each time it has its annual MOT the tester has to ensure that it is maintaining the required revs when checking emissions; it was originally stated that it's due to the "fly by wire" type throttle control and isn't an unexpected situation.
Whether, of course, this is correct about FBW I'm not sure.
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